On Thu, May 12, 2022 at 08:50:34AM +0200, Heinrich Schuchardt wrote:
> On 5/12/22 04:29, AKASHI Takahiro wrote:
> > Booting from a short-form device path which starts with the first element
> > being a File Path Media Device Path failed because it doesn't contain
> > any valid device with simple file system protocol and efi_dp_find_obj()
> > in efi_load_image_from_path() will return NULL.
> > For instance,
> > /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/Scsi(0,0)/\helloworld.efi
> > -> shortened version: /\helloworld.efi
> >
> > With this patch applied, all the media devices with simple file system
> > protocol are enumerated and the boot manager attempts to boot temporarily
> > generated device paths one-by-one.
> >
> > This new implementation is still a bit incompatible with the UEFI
> > specification in terms of:
> > * not creating real boot options
> > * not try
> > "If a device does not support the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL, but
> > supports the EFI_BLOCK_IO_PROTOCOL protocol, then the EFI Boot Service
> > ConnectController must be called for this device with DriverImageHandle
> > and RemainingDevicePath set to NULL and the Recursive flag is set to
> > TRUE."
>
> We already have the ConnectController() logic in lib/efi_driver/. We
> just have to carry it to all block devices (in a future patch set).
>
> > (See section 3.1.2 "Load Option Processing".)
> >
> > But it still gives us a closer and better solution than the current.
> >
> > Fixes: commit 9cdf470274ff ("efi_loader: support booting via short-form
> > device-path")
> > Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
> > ---
> > lib/efi_loader/efi_bootmgr.c | 98 ++++++++++++++++++++++++++++++++++--
> > 1 file changed, 94 insertions(+), 4 deletions(-)
> >
> > diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
> > index 631a25d76e9e..3608e433503e 100644
> > --- a/lib/efi_loader/efi_bootmgr.c
> > +++ b/lib/efi_loader/efi_bootmgr.c
> > @@ -76,6 +76,91 @@ struct efi_device_path *expand_media_path(struct
> > efi_device_path *device_path)
> > return full_path;
> > }
> >
>
> The logic in this patch looks good to me. Just some nits:
>
> Please, provide a description of the function and its parameters.
I don't think we need a description here because, as you can see,
__try_load() is an inner function and intended to be called only from
try_load_from_short_path(). The purpose of extracting it is to avoid
a duplicated code to go though a list of handles *twice*,
for removable media and for fixed media.
The description of try_load_from_short_path() covers both.
> > +static efi_status_t __try_load(efi_handle_t *fs_handles, efi_uintn_t num,
>
> Please, use a name not starting with underscores conveying what the
> function is good for, e.g. efi_load_from_file_path().
>
> > + struct efi_device_path *fp,
> > + efi_handle_t *handle, bool removable)
> > +{
> > + struct efi_handler *handler;
> > + struct efi_device_path *dp;
> > + int i;
> > + efi_status_t ret;
> > +
> > + for (i = 0; i < num; i++) {
> > + if (removable && !efi_disk_is_removable(fs_handles[i]))
> > + continue;
> > + if (!removable && efi_disk_is_removable(fs_handles[i]))
> > + continue;
> > +
> > + ret = efi_search_protocol(fs_handles[i], &efi_guid_device_path,
> > + &handler);
> > + if (ret != EFI_SUCCESS)
> > + /* unlikely */
>
> If you want to tell the compiler that this path is unlikely:
>
> if (unlikely(ret != EFI_SUCCESS))
>
> But as this code is not called often I would simply remove the comment.
>
> > + continue;
> > +
> > + dp = handler->protocol_interface;
> > + if (!dp)
> > + /* unlikely */
>
> ditto
>
> > + continue;
> > +
> > + dp = efi_dp_append(dp, fp);
>
> You are leaking the original dp here. Please, avoid memory leaks.
Actually, not.
The original dp comes from "handler->protocol_interface" and it should
exist while the associated handle, (fs_handles[i]), exists.
-Takahiro Akashi
>
> > + if (!dp)
> > + /* unlikely */
>
> if (unlikely( ?
>
> > + continue;
> > +
> > + ret = EFI_CALL(efi_load_image(true, efi_root, dp, NULL, 0,
> > + handle));
> > + efi_free_pool(dp);
> > + if (ret == EFI_SUCCESS)
> > + return ret;
> > + }
> > +
> > + return EFI_NOT_FOUND;
> > +}
> > +
> > +/**
> > + * try_load_from_short_path
> > + * @fp: file path
> > + * @handle: pointer to handle for newly installed image
> > + *
> > + * Enumerate all the devices which support file system operations,
> > + * prepend its media device path to the file path, @fp, and
> > + * try to load the file.
> > + * This function should be called when handling a short-form path
> > + * which is starting with a file device path.
> > + *
> > + * Return: status code
> > + */
> > +static efi_status_t try_load_from_short_path(struct efi_device_path *fp,
> > + efi_handle_t *handle)
> > +{
> > + efi_handle_t *fs_handles;
> > + efi_uintn_t num;
> > + efi_status_t ret;
> > +
> > + ret = EFI_CALL(efi_locate_handle_buffer(
> > + BY_PROTOCOL,
> > + &efi_simple_file_system_protocol_guid,
> > + NULL,
> > + &num, &fs_handles));
> > + if (ret != EFI_SUCCESS)
> > + return ret;
> > + if (!num)
> > + return EFI_NOT_FOUND;
> > +
> > + /* removable media first */
> > + ret = __try_load(fs_handles, num, fp, handle, true);
> > + if (ret == EFI_SUCCESS)
> > + goto out;
> > +
> > + /* fixed media */
> > + ret = __try_load(fs_handles, num, fp, handle, false);
> > + if (ret == EFI_SUCCESS)
> > + goto out;
> > +
> > +out:
> > + return ret;
> > +}
> > +
> > /**
> > * try_load_entry() - try to load image for boot option
> > *
> > @@ -116,10 +201,15 @@ static efi_status_t try_load_entry(u16 n,
> > efi_handle_t *handle,
> > log_debug("trying to load \"%ls\" from %pD\n", lo.label,
> > lo.file_path);
> >
> > - file_path = expand_media_path(lo.file_path);
> > - ret = EFI_CALL(efi_load_image(true, efi_root, file_path,
> > - NULL, 0, handle));
> > - efi_free_pool(file_path);
> > + if (EFI_DP_TYPE(lo.file_path, MEDIA_DEVICE, FILE_PATH)) {
> > + /* file_path doesn't contain a device path */
>
> %s/device path/device part/
>
> In UEFI speak a file_path is a device path.
>
> Best regards
>
> Heinrich
>
> > + ret = try_load_from_short_path(lo.file_path, handle);
> > + } else {
> > + file_path = expand_media_path(lo.file_path);
> > + ret = EFI_CALL(efi_load_image(true, efi_root, file_path,
> > + NULL, 0, handle));
> > + efi_free_pool(file_path);
> > + }
> > if (ret != EFI_SUCCESS) {
> > log_warning("Loading %ls '%ls' failed\n",
> > varname, lo.label);
